According to the prior art, reinforcing shapes with a flattened form used for flexible tubes are either S-shaped or Z-shaped and, consequently, are difficult to manufacture and install precisely and stably in a helical wrap, or are U-shaped as disclosed, for example, in FR 2,561,745. However, flattened U-shaped reinforcing shapes do not have optimum performance with a given layer thickness since the U-shaped reinforcing element must be thin in order to receive the arms of adjacent windings.
In the present text, an elongated reinforcing element may be designated by the terms "shaped element" or "shape".